Oxidation of substances suspended or dissolved in a liquid resistant to oxidation



ulg M 1964 M. REIG-IEW E11-AIL 391459075 OXIDATION OF SUSSTANODSSUSPENDED OR DISSOLVED IN A LIQUID RESISTANT To OXIDATION Original FiledNov. 2. 1961 MARTIN REICH E mi' LED UHTERSTENHOEFER Mmmm@ United StatesPatent O M M5076 QXHDA'HQN @F SUBSTANCES SUSPENDED 0R DlSSlNlED EN ALlQUiD RESISTANT Ti) @XEDATKUN Martin Reichert, Frankenthal, Pfalz, andLeo Untersteuhoster, Limburgerhof, Pfalz, Germany, assignors to BadischeAnilln- Sodadllabrilr Aktiengesellschaft, Ludwigshafen (Rhine), GermanyContinuation of application Ser. No. 149,719, Nov. '2, i961. rll`l1isapplication Aug. 7, 1963, Ser. No. 303,713 Claims pricrlt f, applicationGermany Nov. 4, 196i) 4 Claims. (Cl. 23ll) This invention relates to aprocess for the oxidation of substances which are suspended or dissolvedin a liquid resistant to oxidation.

In chemical reactions, there are often formed substances which aredissolved or suspended in a liquid and which are to be oxidized because,for example, they are waste products which must be removed. It is knownto separate such suspended substances from the liquid by filtration andthen oxidize them. This method is, however, very complicated.Diliiculties arise especially in the oxidation of the separated moistsubstances, because the particulate solids are usually present as lumpswith relatively large surface area and, during combustion of the same,uncontrollable high temperature peaks occur which strongly attack thecombustion equipment, for example the grate of a boiler furnace. If theheat evolved is to be utilized, for example for steam generation, theuncontrollable heat of combustion which is occasionally evolved in theoverheated regions makes regular operation impossible, especially whenvarying amounts of sub stance are to be oxidized.

lt is known to treat sulfite waste liquors by evaporating and partlyburning the liquors in an indirectly heated tube or in a combustionchamber, separating the residue from the vapor and burning it. Thismethod has the disadvantage that the residue must be separated from thevapor in a special separation plant.

According to another known process, fuel and air are introducedtangentially into a combustion chamber, while the substances to beburned are injected centrally into the combustion chamber and atomized.This method is known for the oxidation of solid substances, but cannotreadily be adapted for the treatment of substances which are suspendedor dissolved in liquids.

It is an object of the present invention to provide a process for thecomplete combustion of combustible substances contained in a liquid inthe presence of the vapor formed by evaporation of the liquid.

A further object of the invention is to provide a process for theevaporation of liquids containing combustible substances by directtreating by means of hot gases and for the subsequent combustion of thecombustible substances.

Further objects and advantages of our invention will become apparent asthe description proceeds.

The above objects are accomplished and the difficulties of the priorprocesses avoided by introducing the oxidation-resistant liquid whichcontains the substance to be oxidized into a rotation-symmetricalchamber, substantially evaporating the liquid, conveying the residualsubstances further in spiral paths by means of a gas stream, intimatelymixing the said residual substances with oxygen-containing gas by meansof a constriction of the gas stream, and substantially oxidizing them.Substances which can be oxidized with particular advantage by theprocess of our invention include carbon black, acetylene polymers, andpolymers of other organic compounds. Liquids resistant to oxidation are,for example, water and sulfuric acid. The term rotation-symmetrical3,145,076 Patented Aug. 18, 1964 lCC chamber as used herein includes,for example, cylindrical, oval and conical chambers.

It has proved successful to effect mixing of the gas stream and theoxygen-containing gas by means of an orice plate, which subdivides therotation-symmetrical chamber into two zones. In the first zone, mainlyevaporation of the liquid takes place. Oxidation is eflected only partlyin the first Zone, and is completed in the second zone.

rl`he heat required to evaporate the oxidation-resistant liquid isadvantageously produced by means of a burner, the flame of which issupplied with an excess of oxygencontaining gas.

The problem of oxidizing waste substances presents itself, for example,in the removal of by-products in acetylene production. In the thermalcracking of hydrocarbons, for example in the production of acetylene bypartial oxidation of hydrocarbons, by cracking hydrocarbons in anelectric arc or with the aid of solid or gaseous heat carriers, carbonblack is formed which becomes suspended in the quenching water injectedinto the hot gases, in waste water from direct gas coolers and in thewash water from gas filters. The bulk of the carbon black is eliminatedin conventional manner by allowing it to float to the surface andseparating it in the form of a slurry which still contains a largepercentage ot water. Since such carbon-black slurries cannot bedischarged into drains or allowed to soak away into the ground, attemptshave been made to remove the carbon black by means of a rotary filterand to burn it in the grate of a steam boiler. This method is attendedby the diiilculties mentioned above.

In operation of the process according to this invention, it has beenfound that carbon black in aqueous suspension, which advantageouslycontains such an amount of water that the mixture is still pumpable, forexample to 99% by weight of water, can be burnt completely and withoutoverheating by the method of our invention. When suitable conveying andmetering equipment, for example a screw conveyor, is employed, it isalso possible to introduce a carbon-black slurry containing less than80% by weight of water into the rst zone ot" the combustion chamber andburn it without overheating by the process according to this invention.

Because of the low concentration of carbon black and oxygen completeoxidation cannot, or only with great expenditure of heat, beaccomplished in a chamber which is not subdivided by a constriction, forexample by an orifice plate.

ln the process according to the present invention, mixing of thesubstantially dried carbon black, which is conveyed in spiral paths inthe vicinity of the wall of the combustion chamber, with free oxygen orair is effected by means of an orifice plate provided between the firstand second zones of the chamber. The internal diameter of the orifice isless than that of the two zones of the rotation-symmetrical chamber. Inthe process according to this invention, either all of the fuel requiredfor evaporating the liquid and of the necessary combustion air isintroduced tangentially into a cylindrical antechamber which is providedat the entrance to the first zone and which has a smaller diameter thanthe first zone of the combustion chamber, or the bulk of the fuel andair is supplied tangentially into the antechamber and the remainder isintroduced tangentially into the first zone of the combustion chamber.

The air or oxygen required for oxidation of the carbon black isintroduced tangentially in the same direction of rotation either whollyinto the antechamber or partly into the antechamber and partly into therst zone of the combustion chamber, so that the gases move through thechamber in a spiral course. The combustion gases envelop thecarbon-black suspension, which is injected through an atomizer pipe,preferably centrally, into the first zone of the combustion chamber, andform a ring of iiame whose diameter is approximately the same as theinternal diameter of the said orifice. ln this zone of high temperature,the wet carbon-black particles are substantially dried and move, throughthe rotating combustion gases containing excess oxygen, in spiral pathsin the vicinity of the wall, where they are thrown by centrifugal force,toward the orifice at the end of the first zone of the combustionchamber.

The oxygen-containing combustion gases entrain the carbon-black acrossthe upstream surface of the orifice plate to the edge of the orificenear the center of the chamber. There the two components mix, and thenburn completely and uniformly in the second zone of the combustionchamber.

if necessary, additional fuel and air may be introduced at the peripheryof the first zone in order to achieve cornplete combustion in the secondzone.

Experiments have shown that it is sufficient to maintain a temperatureof 500 to 650 C. in the vicinity of the wall of the first zone, i.e., atemperature slightly below the ignition point of the carbon black. Inthe second zone, a uniform temperature of about 900 to 1,000 C. issetup.

The heat contained in the gases and the heat of condensation of thewater can be used in conventional manner for preheating the aqueoussuspension or for heating the air or the fuel, so that the fuelrequirements of the process can be kept at a minimum. This heat may alsobe ernployed for heating water or other media.

The heating of aqueous carbon-black suspensions and the evaporation ofwater from such suspensions by heating in contact with solid surfaces isattended by great difficulties because there is very rapidly formed onthe side of the heating surface facing the suspension, a layer of dry,non-wettable carbon black which extremely impairs the transfer of heatinto the suspension and renders it practically impossible to supply asufficient quantity of heat to the suspension.

We have found that these dimculties are obviated and the heat of theoff-gases is utilized in an especially advantageous manner by bringingthe hot gases leaving the combustion chamber, if desired after passagethrough a heat exchanger, wholly or partly into direct contact with theoxidation-resistant liquid in which the substances to be oxidized aresuspended or dissolved, for example in an immersion vessel. By thismethod, the suspension can be heated and concentrated in a simplemanner. The suspension is maintained at a temperature above the dewpoint of the liquid vapors contained in the said hot gases. The off-gasintroduced into the said liquid is cooled to` this temperature. The heatthereby liberated is utilized for heating the contents of the immersionvessel and for evaporating the liquid from the suspension. In thismanner, the water content of a carbon-black suspension can be reduced,for example, from 94% to 82%, Le., about 71% of the water originallycontained in the suspension can be evaporated. At a water content of94%, the ratio of Waterzcarbon black is 94:6. By reducing the watercontent to 82%, this ratio is changed to 82:18, or

The amount of water corresponding to six parts of carbon black has thusbeen decreased from 94 to about 27.3. This is equivalent to a decreasein the amount of water by about 71%.

To recover the heat of evaporation, the uncondcnsed vapor may beliquefied in a condenser, where the vapors contained in the off-gasesare likewise recovered by condensation. One or more of the media to beintroduced into the combustion chamber may be used as cooling media, orwater may be evaporated. Furthermore, an air or fuel preheater may beprovided ahead of the direct heat exchanger.

It is expedient to concentrate the aqueous suspension only to such anextent that it is still pumpable and can be injected into the combustionchamber through an atomizer provided at the top thereof. When thesuspension is highly concentrated, part or all of the air required forcombustion may be used to convey the mixture of carbon black and water.

The process according to this invention permits simple regulation of thefuel supply, in that the additional supply of fuel required when thequantity or the water content of the suspension varies is controlled independence on the off-gas temperature or the temperature prevailing inone of the two zones of the combustion chamber. Automatic control of theprocess is thus rendered possible. It is advantageous to conduct theprocess according to this invention under increased pressure'. Thispermits production of low-pressure steam by condensation of the steamcontained in the off-gas.

In a similar manner, other types of impurities, such as organic matter,can be removed, for example from sulfuric acid or other liquidsresistant to oxidation.

An embodiment of apparatus suitable for carrying out the processaccording to this invention is illustrated, in diagrammatic form and byway of example, in the accompanying drawing.

lnto a vertical cylindrical chamber 1, which is subdivided into twozones 2 and 3 by an orifice plate 11 and provided with a superimposedsmaller cylindrical antechamber 7, gaseous, liquid or solid fuels aresupplied tangentially at 9 and gaseous oxidizing agents are introducedtangentially at 10 in such an amount that the fuel is burned completelyand an excess of oxygen is present in the rotating hot combustion gasfor oxidation of the substances to be oxidized. A suspension or solutionof the substances to be oxidized is injected through an atomizer pipe 8in the direction of the axis of the cylinder. The atomized particles areentrained by the rotating hot combustion gas, and the liquid containedin the particles is substantially evaporated. Deposit formation on thewall of the chamber is thus prevented. Partial oxidation takes placealready during evaporation of the liquid, In the first zone 2, thepartly oxidized substance contained in the suspension is thrown into thevicinity of the wall by centrifugal force and entrained downwardly bythe hot gas in a spiral path to the orifice plate 11. When thetangential speed of the oxidizing agent is suiiiciently high,

, combustion of the fuel takes place mainly in a ring of flame whosediameter is approximately the same as the internal diameter of theorifice plate 11. Excess oxidizing agent added in one or more separateplanes, for example 15 or 16, rotates however mainly in the Vicinity ofthe cylindrical wall and cools the same. At the inner edge of theorifice plate 11, the oxidizing agent streaming toward the centerentrains the particulate solid into the center of the chamber and mixeswith the same, mainly at the edge of the orifice plate. The particulatesolid reacts with the oxidizing agent in the second zone 3, whoseinternal diameter is the same or, advantageously, smaller than that ofthe first zone 2. In the second zone, a high temperature occurs, whichis uniformly distributed over the cross-section of the chamber. Thechamber 1 discharges tangentially to a cylindrical afterburner 4 inwhich any incomplete oxidation is taken to completion. The suspension 17is concentrated in an immersion vessel 5. The recovered liquid iswithdrawn at 12 from a condenser 6. The condenser may be cooled withmedia which are used in the process according to the invention. A heatexchanger 13 is provided for preheating the combustion air and/ or thefuel. The cold off-gases are withdrawn at 14.

The chamber 1 may also be arranged horizontally or in any other positioninstead of vertically. The vertical position is, however, especiallyadvantageous.

Operation of the process according to this invention will be furtherillustrated by the following example, but it is to be understood thatour invention is not limited thereto.

pas

.3 The numbers used in the example correspond with those in theaccompanying drawing.

Example Approx. 170 m3 (S.T.P.)/hr. of coke-oven gas was introduced at9, and approx. 1,300 m.3 (S.T.P.)/hr. of air at i0, into a cylindricalchamber ll whose irst Zone 2 had a diameter of 680 mm. and ya length of1,800 m. 372 kg./ hr. of wet carbon black with a water content of 84.7%was injected axially through an atomizer pipe i5 by means of 150 m3(S.T.P.)/hr. of air.

Halfway up the combustion chamber, a temperature of 630 C. was measuredin the vicinity of the wall.

The carbon black rotating in the vicinity of the Wall was mixed withunconsumed air at the edge of an orifice plate lll of 350 mm. insidediameter, and burnt completely in the second Zone 3 of the chamber ll,which had a length of 2,100 mm. and a diameter of 550 mm. A temperatureof 960 C. was measured at the lower end of this zone.

The oli-gas which had cooled to 610 C. and no longer contained anycarbon black was passed to an immersion vessel S, into which 945 kg. ofwet carbon black with a water content of 94% (S57 kg. dry carbonblack-F888 kg. water) was introduced per hour.

573 kg/hr. of water was evaporated in the immersion vessel 5. This is64.5% of the water contained in the wet carbon-black feed. The oii-gasand the steam left the immersion Vessel at 14 at a temperature of 82 C.372 lig/hr. of concentrated carbonblack suspension with a water contentof 84.7%, which also had a temperature of 82n C., was withdrawn from theimmersion vessel and injected into the cylindrical chamber l asdescribed above.

510 kg./hr. of an aqueous slurry containing 14.1% of dry carbon blackand 2.7% of polymer of higher acetylenes was burned in a similar manner.

This application is a continuation of our application Serial No. 149,719of November 2, 1961, now abandoned.

We claim:

1. A process for the complete combustion of solid waste substances saidsubstances being selected from the group consisting of carbon black andorganic polymers whereby entirely gaseous products are formed, whichprocess comprises: passing said substances incorporated in anoxidation-resistant liquid axially into a first zone of a combustionchamber, tangentially introducing an oxy gen-containing gas and fuelinto an antechamber of said combustion chamber whereby a iiamesupporting gas stream is formed, said gas stream moving in a spiral pathfrom said antechamber through the iirst zone of said combustion chamberin the vicinity of the wall of said combustion chamber, substantiallyevaporating said liquid in said chamber, mixing said waste substancesand said gas stream at a substantial distance from the point ofintroduction of said waste substance and said gas stream into saidchamber, and thereafter passing said intimately mixed substance and gasstream through an orice into a second zone of said chamber whereincomplete combustion of said Waste substance takes place, the internaldiameter of said orifice being substantially less than that of saidfirst and said second zone of said chamber.

2. A process for the complete combustion of carbon black whichcomprises: passing said carbon black suspended in water axially into alirst zone of a combustion chamber, tangentially introducing anoxygen-containing gas and a fuel into an antechamber of said combustionchamber whereby a flame supporting gas stream is formed, said gas streammoving in a spiral path trom said ante chamber through the lirst zone ofsaid combustion chamber in the vicinity of the wall of said combustioncharnber, substantially evaporating said water in said chamber, mixingsaid carbon black and said gas stream at a substantial distance from thepoint of introduction of said carbon black and said gas stream into saidchamber, and thereafter passing said intimately mixed carbon black andgas stream through an orifice into a second zone of said chamber whereincomplete combustion of said carbon black takes place, the internaldiameter of said oriiice being substantially less than that of saidiirst and said second zone of said chamber.

3. A process for the complete combustion of acetylene polymer whichcomprises: passing said acetylene polymer suspended in water axiallyinto a rst zone of a combustion chamber, tangentially introducing anoxygen-containing gas and a fuel into an antechamber of said combustionchamber whereby a iiame supporting gas stream is formed, said gas streammoving in a spiral path from said antechamber through the first zone ofsaid combustion chamber in the vicinity of the wall of said combustionchamber, substantially evaporating said Water in said chamber, mixingsaid acetylene polymer and said gas stream at a substantial distancefrom the point of introduction of said acetylene polymer and .said gasstream into said chamber, and thereafter passing said intimately mixedacetylene polymer and gas stream through an oriice into a second zone ofsaid chamber wherein complete combustion of said acetylene polymer takesplace, the internal diameter of said orifice being substantially lessthan that of said first and said second zone of said chamber.

4. A process as claimed in claim 1 wherein the hot gases leaving thecombustion chamber are brought into direct contact with theoxidation-resistant liquid in which the substances to be oxidixed areincorporated for the purpose of evaporating said liquid.

References Cited in the tile of this patent UNITED STATES PATENTS

1. A PROCESS FOR TH COMPLETE COMBUSTION OF SOLID WASTE SUBSTANCES SAIDSUBSTANCES BEING SELECTED FROM THE GROUP CONSISTING OF CARBON BLACK ANDORGANIC POLYMERS WHEREBY ENTIRELY GASEOUS PRODUCTS ARE FORMED, WHICHPROCESS COMPRISES: PASSING SAID SUBSTANCES INCORPORATED IN ANOXIDATION-RESISTANT LIQUID AXIALLY INTO A FIRST ZONE OF A COMBUSTIONCHAMBER, TANGENTIALY INTRODUCING AN OXYGEN-CONTAINING GAS AND FUEL INTOAN ANTECHAMBER OF SAID COMBUSTION CHAMBER WHEREBY A FLAME SUPPORTING GASSTREAM IS FORMED, SAID GAS STREAM MOVING IN A SPIRAL PATH FROM SAIDANTECHAMBER THROUGH THE FIRST ZONE OF SAID COMBUSTION CHAMBER IN THEVICINITY OF THE WALL OF SAID COMBUSTION CHAMBER, SUBSTANTIALLYEVAPORATING SAID LIQUID IN SAID CHAMBER, MIXING SAID WASTE SUBSTANCESAND SAID GAS STREAM AT A SUBSTANTIAL DISTANCE FROM THE POINT OFINTRODUCTION OF SAID WASTE SUBSTANCE AND SAID GAS STREAM INTO SAIDCHAMBER, AND THEREAFTER PASSING SAID INTIMATELY MIXED SUBSTANCE AND GASSTREAM THROUGH AN ORIFICE INTO A SECOND ZONE OF SAID CHAMBER WHEREINCOMPLETE COMBUSTION OF SAID WASTER SUBSTANCE TAKES PLACE, THE INTERNALDIAMETER OF SAID ORIFICE BEING SUBSTANTIALLY LESS THAN TAHT OF SAIDFIRST AND SAID SECOND ZONE OF SAID CHAMBER.